attribute vec3 vertex;
uniform vec3 eye,ray00,ray01,ray10,ray11;
varying vec3 initialRay;
void main(){
    vec2 percent=vertex.xy*.5+.5;
    initialRay=mix(mix(ray00,ray01,percent.y),mix(ray10,ray11,percent.y),percent.x);
    gl_Position=vec4(vertex,1.);
}